I'm going to play devil's advocate for a moment, as a company trying to downsize it's staff it would make more sense to let the person go that has back issues and only works 3 shifts per week. They could possibly hire a new person to work more shifts and get paid less.

Sorry that you feel betrayed by your job and coworkers. I'm sure everything will work out and I hope this is a blessing in disguise for you and a better, more awesome job is waiting just around the corner for you.